1. Field of the Invention
Various embodiments of the invention relate to the control of the playback of an audio file in real time.
2. Description of the Prior Art
Electronic musical synthesis devices make it possible to play one or more synthetic instruments (produced from acoustic models or from samples or sounds from a piano, a guitar, other string instruments, a saxophone or other wind instruments, etc.) by using an interface for entering notes. The notes entered are converted into signals by a synthesis device connected to the interface by a connector and a software interface using the MIDI (Musical Instrument Digital Interface) standard. An automatic programming of the instrument or instruments makes it possible to generate a series of notes corresponding to a score that can be performed by using software provided for that purpose. Among such software, the MAX/MSP programming software is one of the most widely used and makes it possible to create such a musical score interpretation application. Such an application comprises a graphic programming interface which makes it possible to select and control sequences of notes and to drive the musical synthesis DSP (Digital Signal Processor). In these devices, it is possible to combine a score driven by the interface which controls one of the instruments with a score for other instruments which are played automatically. Rather than controlling synthetic instruments by a MIDI-type interface, it may be desirable to directly control an audio recording, the control making it possible, for example, to act on the playback speed and/or volume of the file. To ensure a musical synchronization of the file which is played with the playing data of the interpreter delivered by the MIDI interface, it would be particularly useful to be able to control the running rate of the score played automatically. The existing devices do not make it possible to provide this control over the playback rate of the different types of audio files used (MP3—MPEG (Moving Picture Expert Group) 1/2 Layer 3, WAV—WAVeform audio format, WMA—Windows Media Audio, etc.) to reproduce prerecorded music on an electronic piece of equipment. There is no prior art device that allows for such real-time control in conditions of musicality that are acceptable.
In particular, PCT application no. WO98/19294 deals only with the control of the playback rate of MIDI files and not of files of signals encoded in a substantially continuous manner such as mp3 or way files.